Inductance core composition



Dec. 24, 1946. H. J. BENNER ETAL 2,413,098

INDUGTANCE CORE COMPOS ITION Filed Jan. 25, 1944 Patented Dec. 24, 1946INDU CTAN CE CORE COMPOSITION Howard J. Benner and Allan M. Hadley,

meadow, Mass., assignors to The F. W. Company, Chicopee, Mass,

Massachusetts Long- Sickles a corporation of Application January 25,1944, Serial No. 519,634

1 Claim. 1 This invention relates to improvements in magnetic meansassociated with an inductance or the like for tuning and controlling thesame and to confine and control the magnetic field thereof.

The principal objects of the invention are directed to a materialadapted for use as cores and closures for inductances which by reason ofits novel characteristics is easily and readily formed thereby tofacilitate speed and economy in man ufacture.

It is known that so-called iron cores have been employed in connectionwith inductance units but the process of producing them requires a moldfor the material consisting of finely ground iron and a binder. Thematerial in the mold is subjected to heat and pressure and the resultingmolded object is hard and brittle and the iron particles are not likelyto be dispersed uniformly therein.

According to this invention, a material is provided which is suitablefor the cores, closures or other parts for inductance coils,transformers and the like. By reason of its novel characteristics thematerial does not have the objectionable hardness and brittleness of theprior art material and not only are the ferrous particles uniformlydispersed therein but parts may be made therefrom in more or less simplemolds and without heat anad pressure. With objects made from thematerial and not having the objectionable hardness and brittleness it ispossible to easily and readily remove portions thereof to change oradjust the characteristics thereof within very narrow limits for tuningand other purposes.

The novel features of the invention are adapted for broad applicationbut will be described in connection with a transformer of theintermediate type and the parts thereof.

In the drawing:

Fig. 1 is a longitudinal sectional view through a transformer embodyingthe novel features of the invention;

Fig. 2 is a sectional view through a unitary inductance and closure; and

Fig. 3 is an end elevational view of an inductance to explain certainfeatures of the invention.

Referring now to the drawing in detail, the invention will be-more fullydescribed.

A transformer 2 is shown in Fig. 1 which includes a tubular metallicouter shell 4 with primary and secondary inductance coils 6 withinclosures 8 in the desired spaced relation. The 010- sures 8 are in tubesIn of dielectric material.

Fixed condensers I2 are provided with terminals I4 and are disposed inopposite ends of the tube 4 with washers i6 placed on the outer sides ofthe condensers. The ends of the tube 4 are deformed in some manner tohold the parts in place. The necessary connections, not shown, areprovided between the inductance coils and. condensers.

The transformer described may be called a fixed-tuned-transforrfieradapted for use as an intermediate transformer in a circuit such as aradio circuit.v As will appear, the transformer not only embodiesv novelfeatures but illustrates in part some of the uses of the material of theinvention.

The so-called iron-cores of the prior art are oftentimes used with aninductance for tuning the same and to tune or vary the value of theinductance the core is moved relative thereto.

In some cases the core is fixed relative to the inductance and tuning isattempted by locating the core of a certain size in a certain wayrelative to the inductance. The characteristics of the cores vary, therelative disposition of the inductance and core is easily changed andthe results are not satisfactory.

According to this invention as shown in Fig. 3, an inductance 6 issupported on a central tube 20 in which is placed as a core the novelmaterial of this invention indicated by 22.

The material for the core of the tube is essentially of a ferrousmagnetic nature and is preferably provided by combining finely powderediron and litharge or lead-monoxide with the aid of glycerine to form asubstantially pasty mixture which is hardenable without the aid of heator pressure.

The iron or its equivalent is powdered to substantially the fineness offlour and with about two parts thereof and one part of litharge the sameare thoroughly mixed with suiiicient glycerine to provide a more or lesspasty composition that is readily manipulated.

The material is poured or in some manner inserted in the tube 20 in anamount to tune the inductance as may be desired. The composition hardensto the desired extent in a few hours but not to the extent that itbecomes brittle or has other undesirable characteristics. The materialadheres sufficiently to the tube to prevent relative movement thereofand with the amount in the tube for a certain result there is nolikelihood of changes in its effects.

The iron particles are uniformly distributed throughout the core andthere being no heat or pressure employed the characteristics thereof areconstant and uniform throughout.

The amount of material in the tube may be varied to provide the desiredtuning effect for the inductance, that is if desired portions of thematerial may be readily removed or additional material added so as toprovide an inductance having the correct and desired value which ismaintained since there are no forces tending to vary the value.

With the prior art iron cores the value of supposedly similar coresvaries so that the accuracy of tuning an inductance is dependent on theaccuracy of the cores.

In many cases it is desirable to enclose an in ductance in a closure toconfine the magnetic field thereof and for other purposes but theclosest approximation to the desired construction has been to provide apair of hollow half parts molded after the manner described inconnection with the prior art ironcores. There are, however, air gaps insuch a construction which are objectionable.

According to this invention, it is possible to completely enclose aninductance with the novel material described- This may be accomplishedin some suitable manner such as by pouring the material into a moldcavity and around the inductance providing a structure such as shown inFig. 2. I

Where the inductance is enclosed it may be desired to connect the coresuch as 22 thereto or in another way a tube such as 20 supporting aninductance may be connected to the closure.

It will be observed that the material of the invention is of such acharacter as to be readily adapted for the uses described as well asother uses and that with the inductance of Fig. 3 it is possible toprovide fixed tuning to the accuracy desired while at the same timeprovide a means of completely sheathing an inductance as in Fig. 2.

The invention may be embodied in other specific forms without departingfrom the essential characteristics thereof. Hence, the presentembodiments are therefore to be considered in all respects merely asbeing illustrative and not as being restrictive, the scope of theinvention being indicated by the appended claim rather than by theforegoing description, and all modifications and variations as fallwithin the meaning and purview and range of equivalency of the appendedclaim are therefore intended to be embraced therein.

What it is desired to claim and secure by Let ters Patent of the UnitedStates is:

A ferrous magnetic non-brittle air hardening composition for tuning aninductance consisting of finely powdered iron two parts, litharge onepart, and suliicient glycerine to render the composition pasty whenfirst mixed and non-brittle when hardened.

HOWARD J. BENNER. ALLAN M. HADLEY.

